Over the past decade, considerable advances have been made in understanding genetic influences on disordered eating. Of particular interest are differential heritability estimates of specific symptoms within each eating disorder diagnostic category. The varying contributions of genes and environment to symptoms within a single diagnostic entity suggests that current research should focus on the symptom level, rather than the diagnostic level, in order to understand the genetic origins of disordered eating and inform treatment interventions. Purging is a highly heritable and readily measurable symptom of eating disorders. Purging can include self-induced vomiting, laxative use, or use of other substances. In addition, although it is classified as a no purging symptom, excessive exercise is a dangerous weight control behavior. Despite the fact that purging is associated with physical and psychological morbidity, only one study has examined the heritability of purging as a distinct phenotype and no studies have examined excessive exercise. Recently, a newly described eating disorder presentation, purging disorder (PD), has been proposed. PD is defined as recurrent purging in the absence of binge episodes. PD currently falls under eating disorder not otherwise specified and may lead to severe medical consequences, including death. To date, little research has examined the prevalence and heritability of PD in large, population-based samples. Understanding genetic factors associated with purging and PD is important, as these factors can influence how eating disorders are recognized, researched, and treated. Insight into familial transmission of many psychiatric disorders has been informed by studies of twins. Thus, the aims of this study are to assess the prevalence of purging behaviors and PD in a large cohort of female twins and to estimate the genetic and environmental contributions to purging behaviors and to PD This project will fill a gap in the research literature by examining the prevalence and heritability of purging behaviors and PD in a large population-based sample of female twins. Learning more about the genetic epidemiology of purging and PD could lead to a greater understanding of core components of eating disorders while helping focus prevention and treatment on environmentally mediated symptoms. [unreadable] [unreadable] [unreadable] [unreadable]